Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$73.44	7.387%	$78.865	$78.87	$78.85	$78.90
Purchase #2	$119.81	3.128%	$123.5577	$123.56	$123.55	$123.60
Purchase #3	$173.92	7.472%	$186.9153	$186.92	$186.90	$186.90
Purchase #4	$221.80	7.482%	$238.3951	$238.40	$238.40	$238.40
Purchase #5	$223.82	5.136%	$235.3154	$235.32	$235.30	$235.30
Purchase #6	$57.28	9.158%	$62.5257	$62.53	$62.55	$62.50
Purchase #7	$191.80	4.684%	$200.7839	$200.78	$200.80	$200.80
7 purchase totals =	$1,061.87		$1,126.3581	$1,126.38	$1,126.35	$1,126.40